template <class InputIterator, class Size, class OutputIterator>
OutputIterator copy_n(InputIterator first, Size count,
OutputIterator result);
Description
Copy_n copies elements from the range [first, first + n) to the
range [result, result + n). That is, it performs the assignments
*result = *first, *(result + 1) = *(first + 1), and so on.
Generally, for every integer i from 0 up to (but not including)
n, copy_n performs the assignment *(result + i) = *(first + i).
Assignments are performed in forward order, i.e. in order of
increasing n. [1]
[1]Copy_n is almost, but not quite, redundant. If first is an
input iterator, as opposed to a forward iterator, then the
copy_n operation can't be expressed in terms of copy.